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The year is 1933.
Swiss astronomer Fritz Zwicky observes galaxy clusters.
I'm not saying galaxies, I'm saying clusters of galaxies.
There, these galaxies are held together by gravity.
The astronomer is trying to find out how fast they are moving.
But he encounters a strange result that he never expected.
The galaxies in the coma cluster are moving very fast.
They move so fast that the mass of the cluster is not large enough to hold those galaxies together.
So why do these galaxies stay there?
In such a case, it seems that we can reach two conclusions.
If this is indeed the case, this cluster is actually not a stable structure, and galaxies will head off somewhere else.
But that does not look like the case.
So there must be an extra gravitational pull from a source we can't see out there somewhere that is preventing them from flying off due to the high velocity.
Maybe his mass estimates of galaxies are wrong.
Of course, he calculates it immediately.
But the result is even more surprising. For those galaxies to stay there without dispersing, 400 times more mass must be there than the astronomer had calculated.
Since He thinks that he has not made such a big mistake in calculation, Zwicky says that there is something dark there that we cannot observe.
Maybe there's something weird going wrong in the Coma cluster in that part of the universe.
Can't it be?
Or Zwicky has unwittingly done something wrong.
Ultimately, this is unexpected.
To claim that, there are 400 times more than what we see.
Moreover, this is such a situation that it can not be explained by planets, meteorites, faint stars or even black holes.
According to star formation models and other observations, we cannot explain the source of this lost mass with known objects.
Then, 3 years after these observations, in 1936, Siclair Smith looks at another galaxy cluster, the Virgo cluster this time.
The result is still the same. 06:36
There, too, there seems to be too much mass to be explained by stars, planets, and black holes.
A lost mass that we cannot see.
Around, 90 years ago, at one hand, evidence is found pointing out that there must have been something out there in the universe; On the other hand, question marks start to rise around the universe, especially in the world of science.
Since there is a loss of mass many times greater than what we see in two different places, where is this missing substance that we can't see?
If we see this in galaxy clusters, shouldn't it be in galaxies themselves too?
Because most of the matter we know is in the galaxies.
Not in the spaces between them.
So let's take a look at the galaxies, shall we?
Where do we start?
From our neighbor, the nearest galaxy to us, Andromeda...
That's what Horace Babcock looked up to in 1939.
If you remember, we looked at the speed of galaxies in a cluster before.
This time, what is looked at is the speed of rotation of a single galaxy around itself.
What did we think in the first place?
Might be unlikely, but maybe galaxy clusters aren't really a cluster.
We said maybe they are falling apart. Can't it? a very clever way to test it out is by observing a galaxy.
Because spiral galaxies like Andromeda are the same all over the universe.
It means they keep their shape.
So they don't fall apart.
That's why it's such a clever test.
So what's the result?
By examining Andromeda's rotation curve, that is, at what speeds it rotates from the center to the very edge, Babcock realizes that the galaxy is spinning much faster than it should.
If Andromeda is somehow able to maintain its structural integrity and spin at that speed, there must be some extra gravitational mass holding it together.
Oh well, Not only do we see this in galaxy clusters, we also observe it in galaxies themselves. Indeed, it's not like that out there, it looks like there's more to it than what we can see.
Calculations of the matter density of the universe today show that 70% of it is made up of dark energy, 25% of it is dark matter, and only 5% of it is that ordinary matter that we know constitutes us.
So 95% of the universe is still a huge mystery.
When we say dark matter, the darkness there comes from this mystery and partly from not interacting with light.
Since we find almost all of the astronomical discoveries we make with classical methods through interactions with light, it is not that easy to detect dark matter.
Do you understand where I'm trying to get to? Or let's put the question this way. Did the scientists understand the conclusion we wanted to reach?
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Researched and written by: Ögetay Kayalı
Presented and Edited by Barış Özcan
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www.barisozcan...